1. Field of the Invention
The present invention pertains, in general, to preparation methods of colloidal crystals used as device materials in optical communication fields, and more specifically, to a method of preparing colloidal crystals for use in manufacturing reflective-mode microdisplays requiring a high efficiency of color display, characterized by forming patterns of photonic crystals including patterns of the crystals with feature size ranged from tens of to hundreds of μm.
2. Description of the Related Art
Generally, colloidal crystals are structured materials in which uniform polymer or inorganic microspheres are arranged into ordered crystalline structure. As such, the crystalline structure resulting from self-organization is face-centered cubic. When the lattice constant of colloidal crystals is the order of the wavelength of light, light within a specific wavelength cannot penetrate but reflected completely by the colloidal crystals. Thus, since the colloidal crystals affect the transmission of light, they are referred to as photonic crystals. At present, many efforts have been made to commercialize the photonic crystals. In this regard, bulk shapes of the colloidal crystals should be controlled to manufacture optical devices, such as optical waveguide or lens.
For patterning of the colloidal photonic crystals, that is, for preparation of patterned photonic crystals in which alternating regions with different photonic band gaps are periodically arranged in the size of tens to hundreds of μm, there is disclosed a method of filling the first particles in microchannels and further filling the second particles each having a different size from that of the first particles between the microchannels (S. M. Yang, H. Miguez, G. A. Ozin, Advanced Functional Materials, 2002, 12, 425). However, this method is disadvantageous in terms of difficulty in repeatedly performing a coating process under complicated conditions. Also, it is impossible to apply the above method to a large area.
In addition, there is proposed a method of patterning a surface and selectively coating particles, by use of a self-assembled monolayer, (Z. -Z. Gu, A. Fujishima, O. Sato, Angew. Chem. Int. Ed. 2002, 41, 2067). But, by the above method, it is difficult to coat multi-layered particles to obtain the desired photonic band gaps. Further, a method of filling the multi-layered particles on previously made patterns is disclosed (S. M. Yang, G. A. Ozin, Chem. Commun. 2000, 2507), but is disadvantageous in terms of selective filling of the particles.